Idle Air Control (IAC) System Monitoring

Requirements
The idle air control system must be monitored for it's ability to maintain a stable idle speed. The system will be considered to be malfunctioning If the difference between actual engine idle speed and the programmed idle speed exceeds fixed limits.

Theory of Diagnostic Operation
The idle air control diagnostic procedure is carried out continuously and compares actual engine idle speed to the idle speed requested by the ECM. It the actual idle speed is lower than 700 rpm or higher than 1200 rpm for two consecutive driving cycles the MIL will be illuminated and a DTC set.

Enabling Criteria
The idle air control diagnostic procedure will run when:

^ Vehicle speed has once exceeded 20 km/h this driving cycle
^ Vehicle speed = 0
^ Coolant temperature >60°C
^ Throttle closed

Hardware Required
No additional hardware is required for this diagnostic.